Enhancement of hydrogen storage properties in 4MgH2- Na3AlH6 composite catalyzed by TiF3

In this work, we have investigated the hydrogen release and uptake pathways storage properties of the MgH2-Na3AlH6 with a molar ratio of 4:1 and doped with 10 wt% of TiF3 using a mechanical alloying method. The doped composite was found to have a significant reduction on the hydrogen release temperature compared to the un-doped composite based on the temperature-programme-desorption result. The first stage of the onset desorption temperature of MgH2-Na3AlH6 was reduced from 170 degrees C to 140 degrees C with the addition of the TiF3 additive. Three dehydrogenation steps with a total of 5.3 wt% of released hydrogen were observed for the MgH2-Na3AlH6-10 wt% TiF3 composite. The re/dehydrogenation kinetics of 4MgH(2)-Na3AlH6 system were significantly improved with the addition of TiF3. Kissinger analyses showed that the apparent activation energy, EA, of the 4MgH(2)-Na3AlH6 doped composite was 124 kJ/mol, 16 kJ/mol and 34 kJ/mol lower for un-doped composite and the as-milled MgH2, respectively. It was believed that the enhancements of the MgH2-Na3AlH6 hydrogen storage properties with the addition of TiF3 were due to formation of the NaF, the AIF(3) and the Al3Ti species. These species may played a synergetic catalytic role in improving the hydrogenation properties of the MgH2-Na3AlH6 system. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.